If you own your practice, whether as a sole proprietor, an S-corp, or a partnership, September 15 is your Q3 estimated tax deadline. It's one of those dates that catches practice owners off guard because it doesn't line up neatly with the rest of the calendar the way most people expect tax deadlines to work.

Estimated taxes exist because the IRS wants its money as you earn it, not once a year in April. A W-2 associate has taxes withheld automatically from every paycheck. As the practice owner, nobody's withholding anything on your behalf, which means sending in your own quarterly payment based on what you expect to owe for the year is entirely on you.

Miss a payment, or underpay by a meaningful amount, and you're looking at a penalty calculated on how much you owed and how late the payment arrived, compounding the longer it goes unpaid. It's not a forgiving calculation.

What we see more often than owners simply forgetting the date is owners who aren't sure what number to actually send in, because their books aren't current enough to calculate it with any confidence. Without knowing your accurate year-to-date net income, you're either guessing low and setting yourself up for a penalty, or guessing high and tying up cash you need for payroll and rent.

This is exactly why we push practice clients to stay current on bookkeeping month to month instead of trying to reconstruct the whole picture every quarter under deadline pressure. When your P&L is accurate as of today, calculating your Q3 payment takes minutes instead of a weekend spent digging through statements and insurance remittances.

If you're not confident in what your Q3 payment should be, or you're not sure you've set aside enough throughout the year, now is the time to find out, not after the 15th has already passed.

Jeremy Brewer is the founder of 911 Bookkeepers LLC in Baton Rouge, Louisiana. 911 Bookkeepers partners with MBJA Accounting Service to give chiropractic and MDVIP practices clean, current financials. He is a Xero Certified Advisor.